High-pressure low-temeprature electrical properties of template-synthesized polypyrrole at low synthesis temperature: dimensional crossover under pressure

摘要

We have measured the pressure and temperature dependence of the electrical conductivity of thin films composed of doped polypyrrole microtubules with a diameter of 400 nm. The microtubules have been synthesized at 0 deg C in a host membrane. The wall thickness of these microtubules can be controlled by a variation of the synthesis time. The results of these measurements are interpreted using the Mott Variable Range Hopping model. Samples composed of thin wall microtubules show a higher characteristic dimension of the conduction process than samples composed of thick wall microtubules. Under pressure, the dimension of the hopping process increases and three-dimensional behavior prevails for all investigated wall thicknesses of the microtubules. Under pressure samples composed of thin wall microtubules show also a change of the temperature dependence of the pre-exponential factor in the Mott law. The results suggest that the microtubules are not homogeneous but are composed of layers with different electrical conductivity behavior.